Of those, one in ten still exceeded the federal cleanup level that the work was supposed to eliminate. The Centers for Disease Control and Prevention has twice lowered what it considers a high blood lead level over the last 15 years. Soil lead can adhere to root vegetables and leafy greens grown in it, and disturbing soil raises dust. Of 388 homes tested inside the Omaha Lead Superfund Site, 208 exceeded 100 parts per million of lead in soil. Among 150 previously remediated yards, one in ten still exceeded the 400 parts per million cleanup level.